Human Physiology The Nervous System.pptx dr sfg

Human Physiology:
The Nervous System
By: Dr. Salem Gerbadi

The Nervous system is:
• A physically connected network of cells,
tissues and organs that allow us to
communicate with and react to the
environment and perform life activities.

Cool Nervous System Facts:
• As a fetus in the womb, neurons develop at
the rate of 250,000 per minute.
• We have about 100 billion nerve cells in our
brain by adulthood (over 600 miles worth) –
yet we typically use around 4% at any given
time
• Neurons are our largest cells
• Messages transmit at speeds up of to 180 MPH

FOUR PRIMARY FUNCTIONS OF
NERVOUS SYSTEM
1. Sensing the world
 Vision, Hearing, Smell, Taste, Touch
2. Transmitting information
3. Processing information
4. Producing a response

The functional unit of the
nervous system is the
nerve cell, the NEURON
They send
electrochemical
messages around the
body
Glial cells provide support
and protection for neurons

Parts of nerve cell
 Dendrites : receive chemical signals from
neighboring cells.
 Cell Body: contains the nucleus & organelles
 Axon: long extension that carries electrical
messages away from the body to the terminal
axons
 Terminal Axons: passes the signal to the next
cell.
 Myelin sheath: Protective covering for axon
 The Synapse The junction between two
communicating neurons

3 main types of neurons:
Sensory neuron = detect stimuli
Interneurons = relay sensory signals to
brain then return message back to motor
neurons.
Motor neuron = pass message from brain
to rest of body for muscle response
This coordinated pathway is known as the
REFLEX ARC
Types of Neurons

Reflex Arc
“ what happens when you step on a nail”?
 Reflexes are automatic
 The Stimulus (nail ) is received
by the sensory neurons in the
foot
 This info travels to the spine,
where the interneuron is triggered
 The interneuron transmits signal
to brain (through the spinal
cord)and carries message back
and stimulates the motor neuron,
to move the foot

A progressive wave of electric and
chemical activity along a nerve fiber
that stimulates or inhibits the action of
a muscle, gland, or other nerve cell
*This is how the information moves from sensory
neurons to interneuron to motor neurons

Nervous System
Has two main divisions
1. Central Nervous System
( CNS) brain, spinal cord
2. Peripheral Nervous System
( PNS) all other nerves

Central Nervous System
(CNS)
Receives, interprets and
sends signals to PNS
Has 2 main parts:
 Brain – main control center
 Spinal Cord – connects and
relays nerve impulses to
the brain
2 MAIN DIVISIONS:

Connects CNS to all organ systems
Made up of:
 Sensory Neurons: detect stimuli
 Motor Neurons: carry signal to stimulate
response
2 major subsystems:
 Somatic – Transmits signals from brain to
voluntary muscles (allows for walking,
talking)
 Autonomic – involuntary movement
(digestion, fight or flight)
Peripheral Nervous System (PNS)

Central Nervous
System
Brain
Cerebrum
Cerebellum
Brain Stem and
Pons
Lobes (4)
Spinal Cord
“information
superhighway”
Peripheral
Autonomic
Sympathetic
 Fight or Flight
Parasympathetic
 Relaxation
Somatic
Sensory and Motor
Nerves
Reflex Arc
Parts of the
Nervous System

•Smaller part of the brain ,towards the
back
FUNCTIONS:
•Coordinates all movement
•Helps maintain posture, muscle control,
and balance

Large front part of the brain
FUNCTIONS:
Voluntary activity
Memory
Language
Receives and responds to sensory signals
Controls motor functions

Top layer of the brain
Stores: experiences and/or learning
Frontal-
behavior &
emotion
Temporal- memory & emotion, speech and hearing
Occipital-
vision
Parietal-
Sensory info
concerning touch

The brain and spinal cord are
surrounded by membranes called
meninges that lie between the
bone and the soft tissues.
Me ning es

BRAIN STEM
 swallowing, coughing,
sneezing, and
vomiting
 Includes the
Medulla Oblongata
PONS
 Breathing
 Heart rate
 Internal Organs
Medulla
• Damage in this area
will usually kill you.

“controls: emotions and memories”
Damage to
these areas
can lead to
amnesia or
emotional
disturbances

Spinal cord
The spinal cord begins at the base of the
brain and extends as a slender cord to
the level of the intervertebral disk
between the first and second lumbar
vertebrae.

Structure of the Spinal Cord
1.The spinal cord consists of 31 segments,
each of which gives rise to a pair of spinal
nerves.
2. A cervical enlargement gives rise to
nerves leading to the upper limbs, and a
lumbar enlargement gives rise to those
innervating the lower
limbs.

3.Two deep longitudinal grooves (anterior
median fissure and posterior median
sulcus) divide the cord into right and left
halves.
4.White matter, made up of bundles of
myelinated nerve fibers (nerve tracts),
surrounds a butterfly-shaped core of gray
matter housing interneurons.
5.A central canal contains cerebrospinal fluid

Ventricles and Cerebrospinal Fluid
1. The ventricles are a series of connected
cavities within the cerebral
hemispheres and brain stem. Are
continuous with the central canal of the
spinal cord, and are filled with
cerebrospinal fluid.
2. Cerebrospinal fluid has nutritive as well
as protective (cushioning) functions

Human Physiology The Nervous System.pptx dr sfg

Human Physiology The Nervous System.pptx dr sfg

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Human Physiology The Nervous System.pptx dr sfg